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    "# Trouble-Shooting Your Setup\n",
    "\n",
    "The code snippets and file system paths here fit an installation according to [1and1/debianized-jupyterhub](https://github.com/1and1/debianized-jupyterhub). If you installed in another way, you have to adapt accordingly."
   ]
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   "cell_type": "markdown",
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   "source": [
    "## Notebooks Don't Open, or Kernel Connection Fails\n",
    "\n",
    "First, look into the log for anything out of the ordinary, using `journalctl -eu jupyterhub`. Also try with an increased log level by setting `JUPYTERHUB_LOGLEVEL=DEBUG` in `/etc/default/jupyterhub`, and then restarting the hub service with `systemctl restart jupyterhub`.\n",
    "\n",
    "If you cannot see anything in the journal, the best route is to get more visibility and direct control by running a notebook server manually, in a shell prompt for your user account."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "First, create a local configuration file.\n",
    "\n",
    "    /opt/venvs/jupyterhub/bin/jupyter notebook --generate-config\n",
    "    ${EDITOR:-vi} ~/.jupyter/jupyter_notebook_config.py"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Change these two settings:\n",
    "\n",
    "    c.NotebookApp.allow_remote_access = True\n",
    "    # Use empty string for bind-all, or your hostname\n",
    "    c.NotebookApp.ip = 'localhost'"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Then start a notebook server, its log goes into your console window.\n",
    "\n",
    "    /opt/venvs/jupyterhub/bin/jupyter notebook .\n",
    "    \n",
    "Watch the console for any errors or other diagnostics while you try to reproduce your problem.\n",
    "\n",
    "💡 Use `Ctrl-C` twice to stop the server after you're done."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Finally, move your local configuration out of the way, since it might interfere with *JupyterHub* operations.\n",
    "\n",
    "    ( cd ~/.jupyter && mv jupyter_notebook_config.py jupyter_notebook_config.py,debug )"
   ]
  }
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